Meat is inevitably exposed to microbes as the material is processed or handled. Microbes are part of the natural decay process of organic material and are commonly deposited on meat by contact between the meat and contaminated equipment or other material. Microbes may also be airborne. Although some microbes may be relatively benign, others contribute to spoilage and some can cause serious illness. Lactic acid producing bacteria are examples of benign microbes, while some strains of E. Coli, Salmonella, Listeria, and Staph bacteria are examples of pathogenic microbes which can cause serious illness when ingested by humans.
Even with careful processing practices, meat may be exposed to pathogenic microbes during processing or initial handling. However, the risk of illness from dangerous microbes which may be present in meat is reduced by careful handling and cooking. In larger cuts of meat for example, dangerous microbes may only be present on the surface of the meat and are readily killed in the cooking process.
Comminuted and mixed meats, including ground beef, require more thorough cooking in order to kill dangerous microbes which may be present in the material. The reason for this is that dangerous microbes residing at the surface of a larger piece of meat may be distributed throughout the final comminuted product as the large piece is ground or otherwise cut into smaller pieces and mixed with other pieces. Thorough cooking is required in order to kill microbes residing in the center of a mass of comminuted meat.
Even though the risk from microbes residing in meat is reduced by proper cooking, it is desirable to control the growth of pathogenic microbes and reduce pathogenic microbe content in meat. Various methods have been developed for improving the quality of meat by reducing or controlling pathogenic microbe content in the material. U.S. Pat. No. 5,871,795, to the inventor of the present invention, discloses a method using ammonia to modify the pH of meat. The ammonia treatment disclosed in U.S. Pat. No. 5,871,795 has been shown to decrease pathogenic microbe content in meat, and to inhibit pathogenic microbe growth after treatment.
While the ammoniated (ammonia treated) meat does exhibit decreased pathogenic microbe content, excessive ammonia exposure may have adverse effects on the product. For example, portions of the meat being treated may be overexposed to ammonia while other portions of the meat may be exposed to very little or none of the ammonia. The overexposed portions may absorb sufficient ammonia to affect the taste of the meat and to produce a residual ammonia odor. Underexposed portions of the meat may not exhibit the desired pathogenic microbe inhibiting effect.